GISS "raw" station data – before and after

I’ve been following this issue a few days and looking at a number of stations and had planned to make a detailed post about my findings, but WUWT commenter Steven Douglas posted in comments about this curious change in GISS data recently, and it got picked up by Kate at SDA, which necessitated me commenting on it now. This goes back to the beginning days of surfacestations.org in June 2007 and the second station I surveyed.

Remember Orland? That nicely sited station with a long record?

Note the graph I put in place in June 2007 on that image.

Now look at the graph in a blink comparator showing Orland GISS data plotted in June 2007 and today:

NOTE: on some browsers, the blink may not start automatically – if so, click on the image above to see it

The blink comparator was originally by Steven Douglas. However he made a mistake in the “after” image which I have now corrected.What you see above is a graphical fit via bitmap alignment and scaling of the images to fit. This is why the dots and lines appear slightly smaller in the “after” image.  I don’t have the GISS Orland data handy at the moment from 2007, but I did have the GISS station plots from Orland from that time and from the present, downloaded from the GISS website today. If I locate the prior Orland data, I’ll redo the blink comparator.

I believe this blink comparator representation accurately reflects the change in the Orland data, even is the dots and lines aren’t exactly the same thickness.

Douglas writes in his notice to me:

It appears that RAW station plots are no longer available, although NASA GISS (Hansen et al) do not say it in this way. Here is the notice on their site:

Note to prior users: We no longer include data adjusted by GHCN and have renamed the middle option (old name: prior to homogeneity adjustment).

I don’t know about the “renamed” option, but the RAW data appears to be NO LONGER AVAILABLE.

Here’s a detailed blink comparison of Orland. All their options now give you an “adjusted” plot of some kind. The “AFTER” in this graph show the “adjustments” to Orland.

Here is what the GISS data selector looks like now, yellow highlight mine, click to enlarge:

Above clip from: http://data.giss.nasa.gov/gistemp/station_data/

Here is the “raw” GISS data plot of Orland I saved back in 2007:

And here is another blink comparator of Orland raw -vs- homogenized data posted by surfacestations.org volunteer Mike McMillan on 12/29/2008:

And here is the “raw” GISS data for Orland today, please note the vertical scale is now different since the pre-1900 data has been removed, the GISS plotting software autoscales to the most appropriate range:

Source:

http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=425725910040&data_set=0&num_neighbors=1

And it is not just Orland, I’m seeing this issue at other stations too.

For example Fairmont, CA another well sited station well isolated, and with a long record:

Here is Fairmont “raw” from 11/17/2007:

And here is Fairmont from GISS today:

Source:

http://data.giss.nasa.gov/cgi-bin/gistemp/gistemp_station.py?id=425723830010&data_set=0&num_neighbors=1

This raises a number of questions. for example: Why is data truncated pre-1900? Why did the slope change? The change appears to have been fairly recent, within the last month. I tried to pinpoint it using the “wayback machine” but apparently because this page:

http://data.giss.nasa.gov/gistemp/station_data/

is forms based, the change in this phrase:

Note to prior users: We no longer include data adjusted by GHCN and have renamed the middle option (old name: prior to homogeneity adjustment).

Appears to span the entire “wayback machine” archive, even prior to 2007. If anyone has a screen cap of this page prior to the change or can help pinpoint the date of the change, please let me know.

It is important to note that the issue may not be with GISS, but upstream at GHCN data managed by NCDC/NOAA. Further investigation is needed to found out where the main change has occurred. It appears this is a system wide change.

The timing could not be worse for public confidence in climate data.

I’ll have more on this as we learn more about this data change.

UPDATE1 from comments:

GISS also just started using USHCN_V2 last month. See under “What’s New”:

http://data.giss.nasa.gov/gistemp/graphs/

“Nov. 14, 2009: USHCN_V2 is now used rather than the older version 1. The only visible effect is a slight increase of the US trend after year 2000 due to the fact that NOAA extended the TOBS and other adjustment to those years.

Sep. 11, 2009: NOAA NCDC provided an updated file on Sept. 9 of the GHCN data used in our analysis. The new file has increased data quality checks in the tropics. Beginning Sept. 11 the GISS analysis uses the new NOAA data set. ”

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